Milo g



(No Model.)

M. G. KELLOGG.

- MULTIPLE SWITGHBOARD.

Patented Oct. 26, 1897-.

l' 1111 L i a z UNITED STATES PATENT Orrrcn.

MILO GHKELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGGSlVITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

M ULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent N 0. 592,353, dated October26, 1897.

' Application fil d January 4,1890. Serial No. 835,862. (No model.)

To all whom 2115 may concern;

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cookand State of Illinois, temporarily residing at Stuttgart, in the Empireof Germany, have invented certain new and useful Improvements inMultiple Switchboards for Telephone-Exchanges, of which the followingisa full, clear, concise, and exact description, reference being had tothe accompanying drawings, forming a part of this specification.

My invention relates to a telephone exchange system in which the linesare singlecircuit lines, grounded at their outer ends; and it consistsin apparatus for switching such lines of the exchange in the operationof the exchange system and a system of test ing the lines to determinewhether they are in use.

In the drawings illustrating my invention, Figures 1 and 1 representsections of two multiple switchboards of the exchange to which the samelines are connected. Fig. 2 shows a diagram of the boards with themainline apparatus and connections necessary to illustrate my invention.Fig. 2 is a detail view of one of the line-annunciators. Fig. 3 shows adiagram of an operators cord system to be used in connection with theboards. Fig. 4. shows an operators test system to be used at the boards.

In Fig. 2 A, is a sectional view of the switchboard shown in Fig. 1, andA is a sectional view of the switchboard shown in Fig. 1", each asindicated by'the line 61 e.

I place as many boards in the central office as are found necessary ordesirable in order to properly operate the exchange. On each board is aspring-jack or other suitable switch for each line. Each switch has acontactspring which normally connects with an insulated contact-pieceand is adapted to receive a loop-plug and, when a plug is inserted, todisconnect the spring from the contact-piece and connect the twocontact-pieces of the plug with the spring and said insulatedcontact-piece,respectively. The switch is also adapted to receive asingle-contact switch-plug, and when a plug is inserted to disconnectthe spring from the contact-piece and connect the spring with thecontact-piece of the plug. In the construction of the switches as shownand as will hereinafter be described I prefer to have a contact-pointelectrically connected with the contact-piece and on which the springnormally bears, as there is less chance of poor connection when thespring bears on a point than when it bears on a surface adapted to bebrought into connection with the plug-contacts.

In Fig. 2, g 9 represent the springs of the different switches, h h thecontact-points 011 which the springs normally bear, and j j thecontact-pieces of the switches, connected with the points h h. Z Z arethe switch-holes. a b are the rubber strips on which the metal parts ofthe switches are mounted, as shown, and through the fronts of which arethe switchholes Z Z. The contact-pieces jj are so placed along one ofthe surfaces of the plug-holes as readily to form connection with one ofthe contact-pieces of the loop-plugs. The holes ZZ are adapted toreceive the switch-plugs shown in Fig. 3 and marked D D, and when a plugis inserted into a switch it raises the spring 9 from the contact-pointh, and the spring g and contact-piece of the plug are in contact. Theseholes are also adapted to receive the loop-plug shown in Fig. 4, and

when a plug is inserted into a hole it raises the spring of the switchfrom the contactpoint h and the spring g and the contactpiece j of theswitch are in contact with the two contact-pieces of the plug,respectively.

w and a: are calling-annunciators, one for each of the lines shown. Eachannunciator has a pair of contact-points normally (or when theannunciator does not indicate a call) in contact with each other, butwhich are separated by the annunciator while it indicates a call. Thetwo contact'points of a pair are marked 12 and q, respectively. One ofthem, q, is a spring-contact which is pressed by the annunciator-dropwhen the drop falls away from its corresponding contact-point p. The

contact-point p is represented as an anglepiece which passes over thespring (1 and is in contact with the spring when the spring is notactuated by the annunciator-drop.

The annunciator is shown in detail in Fig. 2. The line runs to aninsulated bolt 0 at the top of the annunciatouplate o, thence throughthe annunciator-coil to the plate, and

thence normally through spring g, which is in electrical contact withthe plate, to the insulated angle-piece p, and thence to earth.

Two lines are shown in the drawings, one marked line No. 1 and the otherline No. 2. These lines are ordinary single-circuit lines grounded attheir outer ends and having at the subscribers stations any usual andappropriate subscribers-station apparatus. Each line passes successivelythrough the pairs of contacts of its switches on the several boards,passing in each case to the spring first. It then passes through itsline-annunciator and the pair of contact-points of the annunciator tothe ground. The circuit of each line shown may thus be traced in Fig. 2.

In the operators cord system shown in Fig. 3, D D are the switch-plugsof a pair of cords. n n are the rubber insulations of the plugs, and m mare their contact-pieces. These contact-pieces pass eachto the bottom ofits plug and are adapted to rest normally, or

' when the plug is not in use, on the metal it operates the switch, asabove described.

' those skilled in the art.

The plugs should be inserted so that the contact-piece m is in contactwith the spring g.

The connections of the lines might have been reversed, so that the linespass first to the contact-piecej of each of their switches, and in thatcase the plugs should be inserted in such a position that theircontact-pieces form connection with the pieces j of the switches. Y isthe looping-in switch for the pair of cords shown. It is thecalling-key. O is a condenser. R is aresistance-coil, and n is aclearing-out annunciator. t isthe operators telephone, and B is hercalling generator or battery. The circuits are substantially as shown.

The two contact-pieces of the plugs are connected by flexible conductorsto the two levers, respectively, of the looping-in switch. One of thepair of contact-bolts of the switch are connected together through theclearing-out annunciator and the other pair areconnected through theoperators telephone. The lever of the calling-key is connected to one ofthe cords, and the point of the key is grounded through the callinggenerator or battery. The condenser and resistance in parallel with eachother are placed in the circuit of the other cord of the pair.

The. operation of the system in connection with the switchboards will beapparent to It will readily be apparent that when a line is switched bythe insertion of a plug into its switch the line is disconnected i:r(',1nv its normal ground at the central office and is connected into acircuit with the pair of cords and that the circuit of the condenser andresistance-coil of the pair of cords is in its circuit. The condenserand the resistance-coil are connected in multiple or parallel circuit toeach other, as shown. Only one pair of cords is shown, but theconnection of such other pairs with their accompanying apparatus as theoperator may need will be apparent to those skilled in the art. To eachpair of cords, with its plugs, belong a looping in switch, a condenser,a resistance-coil, a clearing-out annunciator, and a calling-key. Onetelephone and one calling-generator will answer for her system of cords.The plugs should be inserted into the switches of the lines, so that thecalling-key is connected to the circuit of the cords between thecondenser and resistance-coil and the switch-plug inserted into the linewhose bell it may be desired to ring. If desired, two calling-keysmay beused for each pair of cords, one connected on each side of thecondenser.

In the operators test system shown in Fig. 4, T is a loop test-plugadapted to be inserted into any of the switches and, when inserted, tooperate them, as heretofore described. B is a test-battery, and S is atest receiving in strument. The battery and instrument are connected ina loop' which terminates in the two contact-pieces of the plug. Eachoperator has one cord system and one test system, and they areconveniently mounted and arranged for her work.

The test receiving instrument and battery are so constructed and relatedto each other that-when they are looped into the circuit with any lineand the circuit is not open at some pair of contact points and does nothave the condenser and resistance-coil in its circuit, as described, theinstrument will sound or respond, but when the circuit is open at anypoint or has a condenser and resistance-coil connected, as described, init the instrument will not sound or respond. This construction dependson the fact that an electromagnet with an armature and a suitableretractile spring may be closed with a battery and a certain resistanceand the armature be attracted, but when the resistance, isconsiderablyincreased (or the circuit opened) the armature will not bemoved. The condenser in the derived circuit offers a circuit for anytelephone-current passing through the lines connected together whichwould otherwise be retarded by the convolutions of the resistance-coil.The resistance-coil afiords a circuit fora clearing-out current sentthrough the circuit, which would, with the condenser only in circuit, beopen to the clearing-out IIC the contact-pieces of the plug. If, then,the

line is not switched at anyswitch and its annunciator does not indicatea call, the instrument and battery are on a closed circuit with the lineand the instrument will sound or respond, indicating that the line isfree to be connected to. If, however, the line-annun- -ciator indicatesa call, (and the line is not switched,) the circuit is open at the pairof annunciator contact-points and the instru ment will not sound. If,again, the line is switched at any board when the test is made and theswitch in which the test is made is in the cut-oh portion of the line,or that portion which is between the switch used for switching and theoliice ground, the test-circuit is open at the pair of contacts 9 h ofthe switch used for switching and the test receiving instrument will notsound. If, again, the line is switched at any board and the test-plug isinserted into a switch which is between the one used and the subscribersstation, the testcircuit has the resistance of the condenser andresistance coil in parallel circuit which is in circuit with the lineand the instrument will not sound. When a test of a line is made and thetest receiving instrument sounds or responds, the operator thereforeknows that neither the line is switched for use at any board nor itsannunciator indicates a call and that she may connect the line withanother. WVhen she makes the test and the instrument does not sound, sheknows that either the line is switched for use at some board or itsannunciator indicates a call and she will not connect it with anotherline. By this system of switching and testing a subscribers line testsbusy when it is switched and when his annunciator indicates a call. Hisline is reserved to himself as soon as he has sent in a call and willnot be switched with another line before his operator has had time toanswer his call, to his confusion and annoyance. In this system alsothere are only two contacts for each line on each board instead of threeor more, as in other systems with ground-circuit lines, and there isonly one wire leading in and one leading out from each switch instead ofthree or more in other systems. There is also but one wire between anytwo boards for each line instead of two or more, as in other systems.

I claim as myinvention and desire to secure by Letters Patent- 1. In atelephone exchange system, a telephone line normally passingsuccessively through pairs of switch contact-points, one pair on each ofseveral boards, each pair normally closed but open while the line isswitched at their board, and through a pair of annunciatorcontact-points normally closed but open while the annunciator indicatesa call, in combination with switching devices at each board todisconnect said pair of contact'points at the board and switch the linefor conversation with a resistance-coil and condenser in multiple orparallel circuit switched into the circuit, and a loop test-plug in thetwo contact-pieces of which terminate the two sides of a loop containinga test receiving instrument and battery, said loopplug being adapted tobe inserted into a switch and when inserted to disconnect said pair ofcontact-points of the switch which are normally in cont-act and connectthem with the two contact-pieces of the plug, said battery andinstrument being so related and adjusted that the instrument sounds whenlooped into the closed circuit of the line without the resistance'eoiland condenser, but does not sound when the resistance-coil andcondenserare included on the circuit, substantially as set forth.

2. In a telephone-exchange system, a telephone-line grounded at itsouter end and normally passing, successively, through pairs of switchcontact-points, one pair on each of several boards, each pair normallyclosed but open while the line is switched at their board, and through apair of annunciator contactpoints normally closed but open while theannunciator indicates a call, and thence to the ground, in combinationwith switching devices at each board to disconnect the pair ofcontact-points at the board and switch the line for conversation with aresistance-coil and condenser in multiple or parallel circuit switchedinto the circuit, and a loop test-plug in the two contact-pieces ofwhich terminate the two sides of a loop containing a test receivinginstrument and battery, said plug being adapted to be inserted into aswitch and when inserted to disconnect said pair of contact-points ofthe switch which are normally in contact and connect them with the twocontact-pieces of the plug, said instrument and battery being so relatedand adjusted that the instrument sounds when they are looped into theclosed circuit of the line, but does not sound when the resistance-coiland condenser are included in the circuit, substantially as set forth.

3. In a telephone-exchange system, a telephone-line normally on closedcircuit and passing successively through pairs of switch contact-points,one pair on each of several boards, each pair normally closed but openwhile the line is switched at their board, and through a pair ofcontact-points of the line annunciator normally in contact but openwhile the annunciatorindicatesa call, in combination with switchingdevices at eachboard to disconnect the pair of contact-points at theboard and switch the line for conversation with a resistance-coil andcondenser in 1nultiple or parallel circuit then switched into thecircuit, and a loop testplug in the two contact -pieces of whichterminate the two sides of a loop containing a test receiving instrumentand battery, said plug being adapted to be inserted into the switchesand when inserted into a switch to disconnect its said pair ofcontact-points and connect them with the two contact-pieces of the plug,said instrument and battery being so related and adjusted that theinstrument 'soundswhen they are looped into the simple closed Circuit ofthe line but will not sound when the resistancecoil and condenser areincluded, substantially as set forth.

4. In a telephone-exchange system, a telephoneline grounded at its outerend and passing normally successively through pairs ofswitch-contact-points, one pair on each of several boards, each pairnormally closed but open while the line is switched at their board, andthrough a pair of contact-points of the line-annunciator normally incontactbut open while the annunciator indicates a call,=and thence tothe ground, in combination with switching devices at each board todisconnect the pair of contact-points at theboard and switch the linefor conversation with a resistance-coil and condenser in multiple orparallel circuit then included in the circuit, a loop test-plug in thetwo contact-pieces of which terminate the two sides of a loop whichcontains a test receiving instrument, said plug being adapted to beinserted into the switches and when inserted into a switch to disconnectits said pair of contact-points and connect them with the twocontact-pieces of the plug, and-batteryin the test circuit therebyestabrelated and adjusted that the instrument sounds when they arelooped into the simple closed circuit of the line but will not soundwhen the resistance-coil and condenser are switched into circuit withtheline, substantially as set forth.

5 In a telephone-exchange system, a tele phone-line normally on closedcircuit and passing successively through pairs of switchcontact-points,- one pair on each of several boards, each pair normallyclosed but open while the line is switched at their board, and through apair of contact-points of the line annunciator normally in contact butopen while the annunciator indicates a call, incombination withswitching devices at each board to disconnect thepair of contact-pointsat the board and switch the line for conversation with. aresistance-coil and condenser in mul-' triple or parallel circuit thenswitched into circuit with it, a loop test-plug in the twocontact-pieces ofwhich terminate the two sides of aloop which contains atest receiving instrument, said plug being adapted to be insertedintothe switches and when inserted into a switch to disconnect its saidpair of contactpoints and connect them with the two contact-pieces ofthe'plug, and battery in the testcircuit thereby established, saidinstrument and battery being so related and adjusted that the"instrument sounds when they are looped into the simple closed circuit ofthe line but will not sound when the resistance-coil and condenser inmultiple or parallel circuit are switched into circuit with the'line,sub stantially as set forth.

6. Inra telephone-exchange system, a telephone-line normally on closedcircuit and havance-coil and condenserin multiple or paral lel circuitthen switched into circuit with it,

p and loop test-plugs, one at each board each plug having twocontact=pieces in which ter ininate the twosides of a loop containing atestreceiving instrument and battery and adapted to be inserted into theswitch of the line at its board, and when inserted to disconnect saidpair of contact-points which are normally in contact and connect themwith the two contact-pieces of the plug, each in-' struinent and itsbattery being so related and adjusted that the instrument sounds whenthey are looped into the simple closed circuit of the line but will notsound when they and the resistance-coil and condenser are switched intocircuit with the" line, substantially as set forth. lished, saidinstrument and battery being so j 7.- ln a telephone-exchange system,- atele g phone-line normally on closed circuit and hav= ing in its circuitpairs of switch contactf points, one pair on each of several boards, 5each pair normally closed but open while the line is switched for use attheir board, and having in its circuit a pair of contact-points l of itsannun'ciator, normally closed but open while the annunciator indicates acall, in com bination with switching devices at each board to disconnectthe pair of contact-points at the i board and connect the line forconversation with a resistance-coil andcondenser in multi 5 ple orparallel circuit then switched into circuit with it, and looptest-plugs, one at each board, each plug having two contact-pieces inwhich terminate the two sides of a loop which contains a test receivinginstrument and adapted to be inserted into the switch of the line at itsboard and when inserted to disconnect the pair of contact-points whichare normally in contact and connect them with the two contact-pieces ofthe plug, and battery in 1 the circuit established on testing, eachinstrument and the battery being so related and adjusted that theinstrument sounds when they are looped into the simple closed circuitofthe line but will not sound when they and the resistance-coil andcondenser are switched into circuit with the line,substantially as setforth. 8. In a telephone-exchange system, multiiple switchboards,telephone-lines, switches for said lines, one switch on each of theboards }for each line, each switch having a pair of contact-pointsnormally in contact but open 5 while aswitch-plug is inserted,line-annunciators, one for each line, each an-nunciator having a pair ofcontact-points normally in contact but open while the an-nun'ciatorindicates a call, each line passing successively through said pairs ofswitch contact points of its switches and through its annunciator andthe annunciator contact-points, in combination with pairs ofswitch-plugs at each board, the contact-pieces of each pair beingconnected by flexible conductors containing a resistancecoil andcondenser in multiple or parallel circuit in their circuit, said plugsbeing adapted to be inserted into the switches at their boards and wheninserted into a switch to disconnect the pair of v contact-points of theswitch and connect the line contact point of the switch with the plugcontact-piece, and loop test-plugs, one at each board, each plug havingtwo contact-pieces in which terminate the two sides of a loop containinga test receiving instrument and battery and adapted to be inserted intoany switch at its board and when inserted into a switch to disconnectthe contact-points of the switch and connect them with thecontact-pieces of the plug, each instrument and its battery being sorelated and adjusted that when they are looped into the simple closedcircuit of any line the instrument will sound but will not sound whenthey and one of said resistance-coils with its condenser are in circuitwith the line, substantially as set forth.

9. In a telephone-exchange system, multiple switchboards,telephone-lines, each line being normally on a closed circuit, switchesfor said lines, one switch on each of the boards for each line, eachswitch having a pair of contact-points normally in contact and openwhile a switch-plug is inserted into its line-annunciators, one for eachline, each annunciator having a pair of contact-points normally incontact but open while the annunciator indicates a call, each linepassing normally successively through said pairs of contact-points ofits switches on the several boards and through its annunciator and thecontact-points of the annunciator, in combination with pairs ofswitch-plugs at each board, the contact-pieces of each pair beingconnected by a flexible conductor containing a resistance-coil andcondenser in multiple or parallel circuit in the circuit, said plugsbeing adapted to be inserted into the switches at their boards and whena plug is inserted into a switch to disconnect the pair ofcontact-points of the switch and connect the line contactpoint of theswitch with the plug contact-piece, and loop test-plugs, one at eachboard, each plug having two contact-pieces in which terminate the twosides of a loop containing a test receiving instrument and battery, andadapted to be inserted into any switch at its board and when inserted todisconnect the contact-points of the switch and connect them with thecontact-pieces of the plug, each instrument and its battery being sorelated and adjusted that when they are looped into the simple closedcircuit of any line the instrument will sound but will not sound whenthe instrument and battery are included in the circuit of the line withany of said resistance-coils with its condenser, substantially as setforth.

In witness whereof I hereunto subscribe my name this 13th day ofDecember, 1889.

MILO G. KELLOGG. lVitnesses:

EMIL ABENHEIM, MARGARETHA Rim-1L.

